Angular 2 Interview Questions and Answers

AngularJS (commonly referred to as “Angular.js” or “AngularJS 1.X”) is a JavaScript-based open-source front-end web application framework mainly maintained by Google and by a community of individuals and corporations to address many of the challenges encountered in developing single-page applications.

Angular (“Angular 2+” or “Angular 2”) is a Typescript-based open-source front-end web application platform led by the Angular Team at Google and by a community of individuals and corporations. Angular is a complete rewrite from the same team that built AngularJS.

Angular 2 was released in late 2016 and brought Angular into the modern web with its desktop and mobile applications.

Angular 4 is backward compatible with Angular 2. Angular 4 is a JavaScript framework for building web applications and apps in JavaScript, html, and TypeScript, which is a superset of JavaScript. Angular provides built-in features for animation, http service, and materials which in turn has features such as auto-complete, navigation, toolbar, menus, etc. The code is written in TypeScript, which compiles to JavaScript and displays the same in the browser. The final version was released on March 23, 2017.

Angular 5 was released on November 1, 2017. It include support for progressive web apps, a build optimizer and improvements related to Material Design.

Angular 6 release will be pushed back to March or April 2018, with Angular 7 showing up in September or October 2018. Each version is expected to be backward-compatible with the prior release. Google pledged to do twice-a-year upgrades.

AngularJS is a structured, JavaScript framework used for dynamic one-page applications. It is a library written in JavaScript. Being a framework, it uses code templates written in HTML in order to perform particular function or command. The data binding and dependency functionalities of Angular JS saves time invested in writing lengthy codes. All these features are packaged in a browser that makes it a suitable server technology.

There are many front-end JavaScript frameworks to choose from today, each with its own set of trade-offs. A truly write less and do more framework. Angular.js uses Plain Old JavaScript Objects (POJO) to share data between different layers of MVC. Many Java based applications are being converted to Angular.js based UI. HTML is great for declaring static documents, but it falters when we try to use it for declaring dynamic views in web-applications. AngularJS lets you extend HTML vocabulary for your application. The resulting environment is extraordinarily expressive, readable, and quick to develop.

Many people were happy with the functionality that Angular 1.x afforded them. Angular 2 improved on that functionality and made it faster, more scalable and more modern. The first release of Angular provided programmers with the tools to develop and architect large scale JavaScript applications, but its age has revealed a number of flaws and sharp edges. Organizations that found value in Angular 1.x will find more value in Angular 2.

The new versions of Angular are now simply called, Angular. Angular 2 is a TypeScript-based, web application development platform that makes the switch from MVC (model-view-controller) to a components-based approach to web development. Angular 2 also offered a much cleaner component model. Interoperation with technologies such as web components was also a focus in Angular 2.

Angular Version 2, first announced in late 2014, finally released in late 2016, marks the beginning of a new platform, not merely a browser bound framework. With Angular you can target browser, mobile (Ionic), desktop (Electron), and server-rendered (Universal) apps.

Angular 2 is high performance and it minimizes the load time of your pages. It is based on TypeScript. Improved Mobile development and web development. It Support for a component-based architecture and all browsers support. Improved data binding and Dependency Injection

Services to encapsulate and reuse non-view related logic that can be used by different parts of an application

Directives Dependency Injection to inject the necessary dependencies for a given component/service at runtime and provide flexibility, extensibility and testability to the framework and your application

TypeScript is a superset of JavaScript but like Java it allows us to define new types. Declaring variables with types rather than the generic var opens the door to new tooling support, which we will find to be a great productivity enhancer. TypeScript comes with a static code analyzer, and as we enter code in our TypeScript-aware IDE (WebStorm/IntelliJ Idea, Visual Studio Code, Sublime Text, etc.) we’re guided by context sensitive help suggesting the available methods in the object or types of the function argument. If we accidentally use an incorrect type, the IDE will highlight the erroneous code.

TypeScript is a strict superset of ECMAScript 2015, which is itself a superset of ECMAScript 5, commonly referred to as JavaScript. As such, a JavaScript program is also a valid TypeScript program, and a TypeScript program can seamlessly consume JavaScript.

In Angular 2, a template is a HTML view that tells Angular 2, how to render your components in the views. The Angular 2 templates are very similar to Angular 1 but Angular 2 have some small syntactical changes.

Shadow DOM is a part of the HTML spec which allows developers to encapsulate their HTML markup, CSS styles and JavaScript. Shadow DOM, along with a few other technologies, gives developers the ability to build their own 1st class tags, web components and APIs just like the <audio> tag. Collectively, these new tags and APIs are referred to as Web Components. Shadow DOM provides better separation of concern along with lesser conflict of styles and scripts with other HTML DOM elements.

@NgModule is a decorator function. A decorator function allows users to mark something as Angular 2 thing (could be a module or component or something else) and it enables you to provide additional data that determines how this Angular 2 thing will be processed, instantiated and used at the runtime. So, whenever user writes @NgModule, it tells the Angular 2 module, what’s going to be included and used in and using this module.

services are reusable function which include their properties used to perform some common functionality which can be used by different components instead of writing the same code again and again for different components a data service can be used by multiple components (via dependency injection).

Angular 2 doesn’t have bi-directional digest cycle, unlike angular 1. In angular 2, any change occurred in the component always gets propagated from the current component to all its children in hierarchy. If the change from one component needs to be reflected to any of its parent component in hierarchy, we can emit the event by using Event Emitter API.

In short, EventEmitter is class defined in @angular/core module which can be used by components and directives to emit custom events.

@output () something Changed = new EventEmitter ();

We use somethingChanged.emit (value) method to emit the event. This is usually done in setter when the value is being changed in the class.

This event emit can be subscribed by any component of the module by using subscribe method.

Angular is based on Components, as Components are the logical piece of code, which consists of Classes, Template and Metadata. tro say more simplistically Components are used to bind model and template while also providing the logical part.

In Angular 2, AOT (Ahead of Time) compilation, in which the angular compiler compiles the angular components and templates to native JavaScript and HTML during the build time. The compiled Html and JavaScript is deployed to the web server so that the compilation and render time can be saved by the browser.

In Angular 2, Change detection basically is the process of detecting the changes in the internal state of our application which might be caused due to Events, XHR and Timers and make it visible in the user interface. Change detection work on the principle of zone.js in Angular.

In Angular 2or 4, Dependency injection gives us the ability to add functionality of a component at runtime. It also provides us a way to create a service that is a reusable piece of code, which can be used across our application to perform a particular function

In Angular 2, PrimeNG is a collection of rich UI components for Angular 2. PrimeNG is a sibling of the popular JavaServer Faces Component Suite, PrimeFaces. All widgets are open source and free to use under Apache License 2.0, a commercial friendly license. PrimeNG is developed by PrimeTek Informatics, a company with years of expertise in developing open source UI components. AngularJS makes it possible to use predefined components for development like tables etc. This helps developers save time and efforts. Using PrimeNG developers can create awesome applications in no time

Decorators are used as identifier of class or type of object that is being created in TypeScript. Angular 2 identifies class below decorator call as definition of class and extend decorator specific properties with class definition.

Lazy loading modules speeds up our applications startup time. Lazy loading creates multiple bundles and loads them on demand in runtime. If we had loaded all our components and templates into one big bundle, it would lead to a large performance penalty.

In Angular 2,@ViewChild decorator is used when a parent component needs to communicate with and pass data to the child component. We need to pass the class name of the child component to @Viewchild decorator function.

Traceur is a JavaScript. Next-to-JavaScript-of-today compiler that allows you to use features from the future today. Traceur supports ES6 as well as some experimental ES.next features. Traceur’s goal is to inform the design of new JavaScript features which are only valuable if they allow you to write better code.

In Angular 2, observables are similar to promises but with major differences that make them better. Observables handle multiple values over time which makes them a good candidate for working with real-time data. Observables can also be cancelled and this gives a better control when working with in-flow of values from a stream. Observables is an ES7 feature which means you need to make use of an external library to use it today. For example, RxJS – https://github.com/Reactive-Extensions/RxJS

Systemjs is a client side module bundler in angular as it loads modules (components and other files) on demand instead of loading an entire application at startup. This largely reduces load times while starting up the app.

The up side of Web pack over Systemjs is that it bundles and creates a single file called bundle.js, which contains HTML, CSS and JS etc. While the initial load time might take a few seconds once the app is cached it becomes lightning fast and will lead to a large boost in performance.

Angular 4 is offered view-engine improvements and code-generation reductions. Angular 4 released in March 2017. The Angular 4.3 upgrade, was released in July and featured HttpClient, which provided a smaller, easier-to-use library for making HTTP requests. Angular 4.3 also has an attribute, @.disabled, for conditionally disabling animations as well as new router life cycle events.

Angular 5’s release took longer than expected, missing previous release targets of September 18 and October 23, 2017.

Angular 5 features are:

Its Simpler Progressive Web Applications.

Making Material Design components compatible with server-side rendering. Google needs to fix a few bugs before releasing this functionality.

A build optimizer that makes the application smaller by eliminating unnecessary code. (The build optimizer is a command-line tool.)

Angular Universal State Transfer API and DOM support

Improved Compiler and Typescript

Pipes for internationalized number, date, and currency

To remove more polyfills, the ReflectiveInjector has been replaced with the StaticInjector. As a result, application size is reduced for most developers.

Multiple names are supported for components and directives, which is useful in helping users migrate without breaking changes.

Updated HTTP client.

CLI 1.5, which generates Angular 5 projects by default.

Router Hooks

The RxJS reactive programming library has been updated to version 5.5.2 or later, featuring operators that eliminate the side effects of code-splitting and tree-shaking problems. Also, RxJS now distributes a version using ECMAScript modules, pulled in by default by the Angular CLI.

Angular version 6 continues an emphasis on being smaller, faster and easier to use. To help achieve these goals, the version 6 beta features a new renderer called Ivy. The beta also adds an optional, backward-compatible generic type to support typed nativeElement. The release candidate for Angular 6 is scheduled for March 2018, with production release on March 28.

AngularJs is a most popular JavaScript framework developed by Google to develop a dynamic web application and mobile application. The AngularJS Development Company makes use of the features provided by the Angular 1.0 to 5.0(next 6, 7, and 8) which brought major improvements of the developed code size. Its every version improved Security and performance.

AngularJS:

It is based on MVC architecture.

It is write in JavaScript to build the application

Two-way data bindings

Attaching new behavior to DOM elements, such as DOM event handling.

Grouping of HTML into reusable components.

Best used tools and support from the Google community

Angular 2 or Angular:

Angular 2 is based on service/controller.

It is write in TypeScript. TypeScript is a superset of JavaScript which helps to build more robust and structured code.

It is Mobile Supported.

Universal server rendering

Improved Data Binding

Data Management

HTTP and more

Angular 4:

It is very Fast and small size

Animations

Email Validator: In Angular 2.0, we use an email validator, using pattern option. But in Angular 4.0, there is a validator to validate an email.

Angular Universal: outside of the browser

Improved overall performance and security

Better Debugging with Source Maps for Templates

Angular 5:

It is Very faster (compare to angualr4). In this loading time as well as execution time has been improved.